One method of transmitting data and other signals is by using twisted wire pair cables. A twisted wire pair cable includes at least one pair of insulated conductors twisted about one another to form a two conductor pair. In practice, most network applications use cables with both solid and stranded conductors. A number of methods known in the art may be employed to arrange and configure the twisted wire pairs into various high-performance transmission cable arrangements. Once the twisted pairs are configured into the desired "core," a plastic jacket is typically extruded over them to maintain their configuration and to function as a protective layer. When more than one twisted pair group is bundled together, the combination is referred to as a multi-pair cable.
In cabling arrangements where the conductors within the wires of the twisted wire pairs are stranded, two different, but interactive sets of twists can be present in the cable configuration. First, there is the twist of the wires that make up the twisted wire pair. Second, within each individual wire of the twisted wire pair, there is the twist of the wire strands that form the conductor. Taken in combination, both sets of twists have an interrelated effect on the data signal being transmitted through the twisted wire pairs.
With multi-pair cables, the signals generated at one end of the cable should ideally arrive at the same time at the opposite end even if they travel along different twisted pair wires. Measured in nanoseconds, the timing difference in signal transmissions between the twisted wire pairs within a cable in response to a generated signal is commonly referred to as "delay skew." Problems arise when the delay skew of the signal transmitted by one twisted wire pair and another is too large and the device receiving the signal is not able to properly reassemble the signal. Such a delay skew results in transmission errors or lost data.
Moreover, as the throughput of data is increased in high-speed data communication applications, delay skew problems can become increasingly magnified. Even the delay in properly reassembling a transmitted signal because of signal skew will significantly and adversely affect signal throughput. Thus, as more complex systems with needs for increased data transmission rates are deployed in networks, a need for improved data transmission has developed. Such complex, higher-speed systems require multi-pair cables with stronger signals, and minimized delay skew.
A number of factors can contribute to the timing differences in signal propagation or skew along different twisted wire pairs in a data transmission cable, each of which may have different lay lengths. Such factors include: the amount or degree of twist or "lay length" of each cable; the geometric configurations of the twisted wire pairs and the cable; the chemical and physical properties of the materials used; and the amount or degree of twist or "lay length" in the wire strands that form the individual conductors of the twisted wire pairs. To better distinguish the "lay length" of the twisted wire pairs from that of the wire strands of the conductors, the lay length of the wire strands will hereinafter be referred to as the "strand twist length."
When twisted wire pair cable s are used in connection with high-speed data communication applications, controlling the various factors that affect signal propagation becomes increasingly important. Thus, there is a need for a twisted wire pair cable that addresses the limitations of the prior art to effectively control and minimize delay skew within multi-pair cables.